Vibration wave motor, linear driving apparatus using vibration wave motor, and optical apparatus

ABSTRACT

In a linear driving apparatus including a vibration wave motor, a sliding guide method is used as a guiding method for a moving member. The apparatus further includes a driving target body movable in a moving direction, a transmission member configured to engage with the driving target body, abut against the abutment part of the moving member, and transmit the driving force of the vibration wave motor to the driving target body, and a biasing member configured to apply a biasing force between the transmission member and the abutment part. The direction of a frictional contact force that the vibrator receives from the friction member and the direction of a biasing contact force that the abutment part receives from the biasing member are parallel and opposite, and the load center of the distribution load of the biasing contact force exists in the range of the outside shape of the vibrator.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a vibration wave motor, a lineardriving apparatus using the vibration wave motor, and an opticalapparatus.

Description of the Related Art

In a conventional ultrasonic motor, a high-frequency voltage is appliedto a piezoelectric element to ultrasonically vibrate a vibrator fixed tothe piezoelectric element. The ultrasonic vibration of the vibratorgenerates a driving force between a friction member and the vibratorpressed against the friction member. This motor can maintain high outputeven in a compact size. For example, Japanese Patent ApplicationLaid-Open No. 2012-16107 discloses an ultrasonic motor using a compactvibrator. In addition, various contrivances for the efficienttransmission of a driving force to a driving target body have beenintroduced into the ultrasonic motor. For example, in the ultrasonicmotor disclosed in Japanese Patent Application Laid-Open No.2014-212682, a rolling member is clamped by the resultant force of apressing force given to the vibrator or its reactive force and thebiasing force of a transmission member supported by a driving targetbody.

In order to downsize and simplify the ultrasonic motor described inJapanese Patent Application Laid-Open No. 2014-212682, there is proposeda sliding structure like that shown in FIG. 11, which is provided withguide shafts 600 extending in the moving direction (the X directionshown in FIG. 11) of a moving member 400, with sliding holes 400 afitted on the guide shafts 600 being formed in the moving member 400. Inthis sliding structure, the guide shafts 600 and the sliding holes 400 aslidably guide the moving member 400. This sliding structure makes itpossible to decide a size 400W in the moving direction X of the movingmember 400 regardless of the movement amount of the moving member 400,and hence to implement the moving member 400 having the same length asthat of the vibrator main body. In addition, since rolling balls can beomitted, the apparatus can be downsized and simplified. In thisarrangement, however, the resultant force of the reactive force of thepressing force given to the vibrator and the biasing force of thetransmission member supported by the driving target body acts as a drag(in a direction vertical to the drawing surface) on the guide shafts 600and the sliding holes 400 a. This increases the frictional force anddecreases the driving force of the ultrasonic motor.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides avibration wave motor which employs a sliding guide and can be downsizedand simplified without reduction in driving force. The present inventionalso provides a linear driving apparatus using such a vibration wavemotor and an optical apparatus.

In order to solve the above problems, there is provided a linear drivingapparatus comprising a vibration wave motor including a vibrator havinga piezoelectric element configured to generate a vibration, a frictionmember configured to come into contact with a protruding portionprovided on the vibrator, a moving member movable in a predeterminedmoving direction with respect to the friction member, a coupling memberconfigured to couple the vibrator and the moving member with each other,a first guide member configured to guide the moving member in the movingdirection, a press member configured to act on the moving member andcapable of moving in the moving direction together with the movingmember, and a second guide member configured to guide the press memberin the moving direction, a driving target body movable in the movingdirection, a transmission member configured to engage with the drivingtarget body, abut against an abutment part of the moving member, andtransmit a driving force of the vibration wave motor to the drivingtarget body, and a biasing member configured to apply a biasing forcebetween the transmission member and the abutment part, wherein adirection of a frictional contact force that the vibrator receives fromthe friction member and a direction of a biasing contact force that theabutment part receives from the biasing member are parallel andopposite, and a load center of a distribution load of the biasingcontact force exists in a range of an outside shape of the vibrator.

According to the present invention, it is possible to provide avibration wave motor which can be downsized and simplified withoutreduction in driving force. It is also possible to provide a lineardriving apparatus using such a vibration wave motor and an opticalapparatus.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded perspective view of a linear driving apparatususing a vibration wave motor 10 according to an embodiment of thepresent invention.

FIG. 1B is a perspective view of the linear driving apparatus.

FIGS. 2A and 2B are perspective views, respectively, of a transmissionmember 18 and a biasing member 19 of the linear driving apparatusaccording the embodiment of the present invention.

FIG. 2C is an enlarged view of an abutment portion.

FIG. 2D is a sectional view of the abutment portion.

FIGS. 3A, 3B, 3C and 3D are views, respectively, showing a state inwhich the transmission member 18 and the biasing member 19 are assembledto the vibration wave motor 10 according to the embodiment of thepresent invention.

FIGS. 4A and 4B are exploded perspective views, respectively, of avibration wave motor 10 according to Example 1 of the present invention.

FIGS. 4C and 4D are exploded perspective views, respectively, of avibrator 1 and a coupling member 5.

FIGS. 5A, 5B, 5C, 5D and 5E are views, respectively, showing a structureand the action of forces according to Example 1 of the presentinvention.

FIGS. 6A, 6B, 6C, 6D and 6E are views, respectively, showing a structureand the action of forces according to Example 2 of the presentinvention.

FIGS. 7A, 7B, 7C, 7D and 7E are views, respectively, showing a structureand the action of forces according to Example 3 of the presentinvention.

FIGS. 8A, 8B, 8C, 8D and 8E are views, respectively, showing a structureand the action of forces according to Example 4 of the presentinvention.

FIGS. 9A and 9B are views, respectively, showing the action of forcesaccording to the first modification of the present invention.

FIGS. 9C and 9D are views, respectively, showing the action of forcesaccording to the second modification of the present invention.

FIG. 10 is a view showing the third modification of the presentinvention.

FIG. 11 is a view showing an example of related art.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail in accordance with the accompanying drawings.

The arrangement of a linear driving apparatus using a vibration wavemotor (ultrasonic motor) 10 according to the present invention will bedescribed below with reference to the accompanying drawings. Assume thatthe moving direction of a vibrator 1 of the vibration wave motor 10 isdefined as the X direction, the direction of the press contact force ofthe vibrator 1 is defined as the Z direction, and a directionperpendicular to the X and Z directions is defined as the Y direction.With regard to all the drawings, the X, Y, and Z directions are definedas described above. Note that as for the Z direction, the verticaldirection is used as needed in accordance with the drawing.

The linear driving apparatus using the vibration wave motor 10 accordingto this embodiment will be described first. FIG. 1A is an explodedperspective view showing the linear driving apparatus using thevibration wave motor 10, which is exploded in the Z direction. FIG. 1Bis a view of a completed linear driving apparatus. A driving target body17 is a member that holds an optical element used for a photographingapparatus as a driving target. The driving target body 17 canreciprocally move in a moving direction X of a moving member 4 whilebeing guided by guide shafts 15 when the vibration wave motor 10 outputsa driving force. The optical element generally means a lens such as afocus lens, but may be a prism or a mirror. Although the embodiment hasexemplified an optical apparatus using the linear driving apparatus inwhich the driving target body 17 functions as a member configured tohold an optical element used for a photographing apparatus, the drivingtarget body 17 can be applied to a component other than the memberconfigured to hold the optical element.

A transmission member 18 is supported by a support portion 17 a of thedriving target body 17. The transmission member 18 is mounted on themoving member 4, together with a biasing member 19, so as to abutagainst an abutment part 4 d of the moving member 4. The linear drivingapparatus using the vibration wave motor 10 in the completed state shownin FIG. 1B is configured such that a driving force is transmitted fromthe vibrator 1 as a drive source (to be described later) to a couplingmember 5, the moving member 4, the abutment part 4 d, the transmissionmember 18, and the driving target body 17 in the order named toreciprocally move the driving target body 17 in the X direction.

FIGS. 2A and 2B are perspective views, respectively, of the transmissionmember 18 and the biasing member 19. FIG. 2A is a view seen from abovein the Z direction. FIG. 2B is a view seen from below in the Zdirection. FIGS. 2C and 2D are enlarged views, respectively, of anabutment portion where the transmission member 18 abuts against theabutment part 4 d of the moving member 4. FIG. 2C is a projection viewseen from the Z direction. FIG. 2D is a sectional view taken along a cutline IID-IID in FIG. 2C. The transmission member 18 is supported by thesupport portion 17 a of the driving target body 17 described above andabuts against the abutment part 4 d of the moving member 4 tosynchronously move the moving member 4 and the driving target body 17.The transmission member 18 has a concave portion 18 a. The concaveportion 18 a is configured to come into biasing contact with theabutment part 4 d. In this embodiment, the transmission member 18 issupported by the support portion 17 a so as to be freely pivotal about ashaft 18 b. It is however possible to select an arrangement in which thetransmission member 18 is supported to be linearly movable. In addition,in the form of this embodiment, a concave shape is formed on thetransmission member 18 side, and a convex shape is formed on theabutment part 4 d side. It is however possible to select a form in whichconvex and concave portions are formed on the opposite sides to those inthe above arrangement.

The biasing member 19 is a torsion coil spring, which applies a biasingforce to the transmission member 18 to provide a biasing contact forceZ11 between the transmission member 18 and the abutment part 4 d. Inthis embodiment, the biasing member 19 is a torsion coil spring.However, it is possible to select a compression spring, tension spring,or leaf spring as long as it can provide the biasing contact force Z11.

Referring to FIG. 2D, the concave portion 18 a has an almost V-shapedcross-section. The biasing contact force Z11 generated by the biasingmember 19 has two distribution load areas M1 and M2 shown in FIG. 2C. Aload center B of the distribution loads corresponds to the midpoint ofthem. Although this embodiment has exemplified the form in which thereare two distribution load areas, even if the number of distribution loadareas changes in accordance with the shapes of the transmission member18 and the abutment part 4 d, the load center B of the distributionloads can be regarded in the same manner.

A mechanism through which the vibration wave motor 10 used for thelinear driving apparatus according to this embodiment transmits adriving force to the driving target body 17 will be described next. FIG.3A is a plan view showing how the transmission member 18 is mounted onthe vibration wave motor 10 and biased by the biasing member 19. FIG. 3Bis a front view of the vibration wave motor 10. FIG. 3C is a sectionalview taken along a cut line IIIC-IIIC in FIG. 3A. FIG. 3D is aperspective view.

Referring to FIG. 3A, the distribution load areas of a frictionalcontact force Z1 between the vibrator 1 and a friction member 2 (to bedescribed later) correspond to the ranges of protruding portions 1 b ofthe vibrator 1. Therefore, the frictional contact force Z1 has twodistribution load areas N1 and N2. A load center A of the distributionload areas corresponds to the midpoint of the distribution loads.Although this embodiment has exemplified the form in which there are twodistribution load areas, even if the number of distribution load areaschanges in accordance with the number of protruding portions 1 b of thevibrator 1, the load center A of the distribution loads can be regardedin the same manner.

FIG. 3D shows how the frictional contact force Z1 and the biasingcontact force Z11 act, and generated couples V1 and V2 act. Note thatthe shift of the relative positional relationship between the frictionalcontact force Z1 and the biasing contact force Z11 is emphaticallyshown. If the load center A of the frictional contact force Z1 coincideswith the load center B of the biasing contact force Z11, the couple V1around the Y-axis almost perpendicular to the moving direction X can bereduced to 0. Likewise, the couple V2 around the X-axis in the movingdirection X can be reduced to 0. The outline of the linear drivingapparatus using the vibration wave motor 10 according to this embodimenthas been described above. Features of the vibration wave motor 10according to each example will be described next.

Example 1

The arrangement of a vibration wave motor 10 according to Example 1which is used for the linear driving apparatus according to theembodiment of the present invention will be described. FIGS. 4A and 4Bare exploded perspective views, respectively, of the vibration wavemotor 10. FIG. 4A is a view seen from above in the Z direction. FIG. 4Bis a view seen from below in the Z direction. FIGS. 4C and 4D areexploded perspective views, respectively, showing enlargement of partsin FIGS. 4A and 4B.

A vibrator 1 is constituted by a piezoelectric element 1 c thatgenerates a vibration, a plate portion 1 a, and two protruding portions1 b. The protruding portions 1 b and the plate portion 1 a can beintegrally molded or assembled as separate components. The piezoelectricelement 1 c has a predetermined area polarized and is attached to theplate portion 1 a. A power feeding means (not shown) applies ahigh-frequency voltage to the piezoelectric element 1 c to generatevibration (ultrasonic vibration) with a frequency in an ultrasonicregion. Since Japanese Patent Application Laid-Open No. 2012-16107 hasdescribed the principle of obtaining a driving force from the vibrator 1by generating this vibration, a description of it will be omitted.Although Example 1 has exemplified the case in which the vibrator 1 hasthe two protruding portions 1 b, the number of protruding portions 1 bis selectable in accordance with a desired driving force. The vibrator 1can reciprocally move in the X direction shown in FIGS. 4A and 4B.

A friction member 2 is arranged to face the vibrator 1 and is fixed tofixing members 8 while being in contact with the vibrator 1. Example 1exemplifies a case in which the friction member 2 has a plate-likeshape. However, a round bar shape or the like can also be selected asthe shape of the friction member 2. In addition, a material such as ametal or ceramic material can be selected for the friction member 2within a range that satisfies requirements for mechanicalcharacteristics such as rigidity and surface properties.

A felt member 7 has a function of giving a press contact force receivedfrom a moving member 14 (to be described later) to the vibrator 1 andalso has a function of preventing attenuation of a vibration. The movingmember 14 can move in a moving direction X of the vibrator 1 withrespect to the friction member 2. The moving member 14 includes slidingparts 14 a and 14 b each having a hole shape in which a first guidemember 6 (to be described later) is fitted, and an abutment part 14 dagainst which a transmission member 18 abuts. The sliding parts 14 a and14 b and the abutment part 14 d can be integrally molded on the movingmember 14 or assembled as separate components.

A coupling member 5 is fixed to the vibrator 1 through first fixingportions 5 a or fixed to the moving member 14 through second fixingportions 5 b to couple the vibrator 1 to the moving member 14. Thismakes it possible to synchronously move the vibrator 1 and the movingmember 14. The coupling member 5 has a property of exhibiting lowrigidity in the Z direction so as not to inhibit a frictional contactforce Z1 between the vibrator 1 and the friction member 2 and exhibitinghigh rigidity in the X direction to allow the vibrator 1 and the movingmember 14 to synchronously move. When being fixed to the vibrator 1through the first fixing portions 5 a, the coupling member 5 is fixed topositions of the vibrator 1 which correspond to nodes of vibration orsimilar portions at which vibration is small by a method like bonding orwelding (not shown). When being fixed to the moving member 14 throughthe second fixing portions 5 b, the coupling member 5 is fixed to themoving member 14 by a method like bonding, welding, or screw fastening(not shown). Example 1 has exemplified the case in which the couplingmember 5 is formed from one member having a frame-like shape. However,the coupling member 5 may be formed from a plurality of members or anarbitrary material and shape can be selected for the coupling member 5within a range that satisfies the requirement for the above rigiditycharacteristic.

The first guide member 6 is a round bar for slidably guiding the movingmember 14 in the X direction. The first guide member 6 is a slidingguide that is fitted in the sliding parts 14 a and 14 b of the movingmember 14 and need not rolling balls and the like. Example 1 exemplifiesa case in which the round bar is used. However, a square bar or platemember can be selected as long as the shapes of the sliding parts 14 aand 14 b are made to comply with the guide member.

A press member 13 is a compression spring that is arranged such that theupper end of the press member 13 acts on the moving member 14, and thelower end acts on an auxiliary moving member 12. The auxiliary movingmember 12 includes a flat portion 12 a and two protruding portions 12 b.The two protruding portions 12 b are fitted in the hole portions of themoving member 14. This fitting allows the movement of the auxiliarymoving member 12 in the Z direction with respect to the moving member 14but restricts the movement in the X direction. Hence, the auxiliarymoving member 12 moves in the X direction together with the movingmember 14. Example 1 has exemplified the case in which the press member13 is the compression spring. However, a tension spring or leaf spring,or a magnet that generates a magnetic force can be selected as long asit can generate a desired force to be described later. Note that themoving member 14 and the auxiliary moving member 12 correspond to afirst moving member and a second moving member, respectively, describedin the appended claims.

A second guide member 16 is a rail-shaped plate member that guides theauxiliary moving member 12 in the X direction. The auxiliary movingmember 12 moves in synchronism with the moving member 14 while makingthe flat portion 12 a slide on the second guide member 16. Example 1 hasexemplified the case in which the flat portion 12 a directly slides onthe second guide member 16. However, an arrangement with a frictionreducing sheet member or rotating roller member provided on the secondguide member 16 can be selected as long as a desired durability issatisfied. An arrangement in which the auxiliary moving member 12 isomitted to make the lower end of the press member 13 directly slide onthe second guide member 16 can also be selected as long as a desireddurability is satisfied. Example 1 has exemplified the case in which thesecond guide member 16 is a plate member. However, any other shape likea round bar member can also be selected.

The fixing members 8 hold the first guide member 6 fitted in two holes 8a and also support the second guide member 16. The fixing members 8 areassembled in an X1 direction shown in FIG. 4A. The friction member 2 isthen fixed to the fixing members 8 by being fastened with screws 9. Thefixing members 8 are supported by a fixing portion (not shown). As aholding method for the first guide member 6 and the second guide member16 and a fixing method for the friction member 2, arbitrary methods canbe selected.

Forces acting inside the vibration wave motor 10 according to Example 1will be described next. FIGS. 5A and 5C are enlarged views,respectively, of a vicinity of the moving member 14 on a plane. FIG. 5Bis a sectional view taken along a cut line VB-VB in FIG. 5A. FIG. 5D isa sectional view taken along a cut line VD-VD in FIG. 5C. FIG. 5E is afront view. The vibrator 1, the felt member 7, the auxiliary movingmember 12, the press member 13, the moving member 14, the transmissionmember 18, and a biasing member 19 are components which move in the Xdirection, to which the friction member 2, the first guide member 6, andthe second guide member 16 are fixed.

External forces acting on the vibrator 1 are the frictional contactforce Z1 that the protruding portions 1 b of the vibrator 1 receive fromthe friction member 2 shown in FIG. 5B, and a contact force Z2 that thepiezoelectric element 1 c of the vibrator 1 receives from the movingmember 14 via the felt member 7. Considering the balance on the X-Zplane of the vibrator 1, the frictional contact force Z1 and the contactforce Z2 are equal in magnitude and opposite in direction. As shown inFIG. 5A, the distribution load areas of the frictional contact force Z1are areas N1 and N2 that are the projections of the protruding portions1 b of the vibrator 1. The load center is a load center A, as describedabove.

External forces acting on the moving member 14 are contact forces Z11,Z12, Z13, and Z14 shown in FIG. 5D. The contact force Z11 (biasingcontact force Z11) is a force that the abutment part 14 d of the movingmember 14 receives from the biasing member 19 via the transmissionmember 18. This force is set by the spring force of the biasing member19. The contact force Z12 is a force that the moving member 14 receivesfrom the vibrator 1 via the felt member 7. Since the contact force Z12is the reaction of the contact force Z2, the contact force Z12 and thecontact force Z2 are equal in magnitude and opposite in direction. Thecontact force Z13 is a force that the moving member 14 receives from thepress member 13. This force is set by the spring force of the pressmember 13. The contact force Z14 is a force that the moving member 14receives from the first guide member 6.

In Example 1, the directions of the forces are illustrated assuming thatthe biasing contact force Z11 is larger than the contact force Z12.Using sizes L1 and L2 shown in FIG. 5D and considering the balance onthe Y-Z plane of the moving member 14, we obtainZ13=(L2/(L1+L2))×(Z11−Z12)  (i)Z14=(L1/L2)×Z13  (ii).

To simplify the calculation, the sizes L1 and L2 in FIG. 5D are assumedto be almost equal. Since the contact force Z12 is equal to thefrictional contact force Z1 in magnitude, as described above, the sum ofthe contact force Z13 and the contact force Z14 equals the differencebetween the frictional contact force Z1 and the biasing contact forceZ11. As shown in FIG. 5C, the distribution load areas of the biasingcontact force Z11 are areas M1 and M2 that are the projections of thecontact areas between the abutment part 14 d and a concave portion 18 aof the transmission member 18. The load center is a load center B, asdescribed above.

A frictional force is generated between the moving member 14 and thefirst guide member 6 by the reaction of the contact force Z14, and africtional force is generated between the auxiliary moving member 12 andthe second guide member 16 by the reaction of the contact force Z13. Asdescribed above, the sum of the contact force Z13 and the contact forceZ14 equals the difference between the frictional contact force Z1 andthe biasing contact force Z11. For this reason, a value obtained bymultiplying the difference by a friction coefficient corresponds to thefrictional force generated by sliding.

Features of Example 1 will be described below. The first feature of thisexample is that the direction of the frictional contact force Z1 thatthe vibrator 1 receives from the friction member 2 and the direction ofthe biasing contact force Z11 that the abutment part 14 d receives fromthe biasing member 19 are parallel and opposite, as shown in FIGS. 5B,5D, and 5E. According to the first feature, the sum of the frictionalforces generated between the moving member 14 and the first guide member6 and between the auxiliary moving member 12 and the second guide member16 equals a value obtained by multiplying the difference between thefrictional contact force Z1 and the biasing contact force Z11 by afriction coefficient. The frictional force serves as a slidingresistance acting when the moving member 14 and the auxiliary movingmember 12 move in the X direction. Hence, if the frictional force issmall, a decrease in the driving force of a motor is suppressed.

The arrangement of Example 1 and the arrangement of a related art (forexample, the arrangement of the related art shown in FIG. 11) will becompared next. In the arrangement of the related art, no rolling ballsare employed on the guide member, and a simple sliding guide is formed.For this reason, a frictional force generated on a guide shaft 600 has avalue obtained by multiplying the sum of the biasing contact force andthe frictional contact force by a friction coefficient. In thearrangement of the related art, the frictional force is large, and thedriving force of the motor thus greatly decreases. Hence, to reduce thefrictional force, rolling balls may be employed. However, when rollingballs are employed, grooves to make the rolling balls roll need to beformed. This makes a size 400W of a moving member 400 in the travelingdirection larger than that of the vibrator, and the apparatus cannot bedownsized and simplified.

In Example 1, however, the frictional force generated on the first guidemember 6 and the second guide member 16 has a value obtained bymultiplying the difference between the biasing contact force Z11 and thefrictional contact force Z1 by a friction coefficient. Hence, since thefrictional force is reduced as compared to the arrangement of therelated art, the driving force of the motor does not decrease even inthe arrangement in which rolling balls need not be employed, and asimple sliding guide is formed. As a result, grooves to make the rollingballs roll need not be formed in the moving member 14. It is thereforepossible to make a size 14W of the moving member 14 in the movingdirection X equal to or smaller than the size of the vibrator 1 in themoving direction X.

The second feature of Example 1 is that the load center A of thedistribution load of the frictional contact force Z1 and the load centerB of the distribution load of the biasing contact force Z11 are alignedon a straight line L along a direction Y perpendicular to both themoving direction X and a direction Z of the frictional contact force Z1,as shown in FIGS. 5A, 5C, and 5E. According to the second feature, sinceno couple V1 around the Y-axis shown in FIG. 5E is generated in themoving member 14, the moving body can reciprocally move with highposition accuracy without tilting around the Y-axis. Note that the loadcenter B of the distribution load of the biasing contact force Z11exists in the range of the outside shape of the vibrator 1.

As described above, the vibration wave motor 10 according to Example 1can use, as the guide method for the moving member 14, a sliding guidecapable of downsizing and simplifying the vibration wave motor withoutdecreasing the driving force of the vibration wave motor 10. Inaddition, the linear driving apparatus can also be downsized andsimplified. In Example 1, on a plane perpendicular to the direction ofthe frictional contact force Z1, the load center A of the distributionload of the frictional contact force Z1 and the load center B of thedistribution load of the biasing contact force Z11 are aligned in themoving direction X, and the load center A and the load center B almostcoincide with each other, as shown in FIGS. 5A and 5C. As a result, thecouple V2 shown in FIG. 5B is hardly generated. Hence, when thefrictional contact force Z1 is made almost equal to the biasing contactforce Z11, the frictional force serving as a sliding resistance isreduced to almost 0. It is therefore possible to reduce a decrease inthe driving force of the vibration wave motor 10 caused by thefrictional force to almost 0.

Note that in Example 1, the effects have been described assuming thatthe sizes L1 and L2 are almost equal. However, even if the sizes L1 andL2 are different, the contact force Z13 and the contact force Z14 aredecided by equations (i) and (ii). Hence, since the frictional forcegenerated on the first guide member 6 and the second guide member 16 hasa value obtained by multiplying the difference between the biasingcontact force Z11 and the frictional contact force Z1 by a frictioncoefficient, the same effects as described above can be obtained.

Example 2

Regarding Example 2, a description of parts common to Example 1 will beomitted, and only different points will be described. In Example 1, thebiasing contact force Z11 is larger than the frictional contact forceZ1, and considering the balance on the X-Z plane of the moving member14, the contact force Z13 acts in the same direction as the frictionalcontact force Z1. On the other hand, in Example 2, a biasing contactforce Z21 is smaller than a frictional contact force Z1, and consideringthe balance on the X-Z plane of a moving member 24, a contact force Z23acts in the same direction as the biasing contact force Z21, as shown inFIGS. 6A to 6E. In Example 2 in which such forces act, the direction inwhich the moving member 24 is pressed by a press member 23 is reverse tothat in Example 1, and the mounting directions of an auxiliary movingmember 22 and a second guide member 26 are also reverse.

As for the above-described arrangement, using sizes L1 and L2 shown inFIG. 6D and considering the balance on the Y-Z plane of the movingmember 24, we obtainZ23=(L2/(L1+L2))×(Z22−Z21)  (iii)Z24=(L1/L2)×Z23  (iv).

To simplify the calculation, the sizes L1 and L2 in FIG. 6D are assumedto be almost equal. Since a contact force Z22 is equal to the frictionalcontact force Z1 in magnitude, as in Example 1, the sum of the contactforce Z23 and a contact force Z24 equals the difference between thefrictional contact force Z1 and the biasing contact force Z21. As aresult, the frictional force as the cause of a decrease in the drivingforce can be reduced, as in Example 1.

As described above, a vibration wave motor 10 having the arrangement ofExample 2 can use, as the guide method for the moving member 24, asliding guide capable of downsizing and simplifying the vibration wavemotor without decreasing the driving force, as in Example 1. Inaddition, the linear driving apparatus can also be downsized andsimplified. Note that in Example 2, the effects have been describedassuming that the sizes L1 and L2 are almost equal. However, even if thesizes L1 and L2 are different, the contact force Z23 and the contactforce Z24 are decided by equations (iii) and (iv). Hence, since thefrictional force generated on a first guide member 6 and the secondguide member 26 has a value obtained by multiplying the differencebetween the biasing contact force Z21 and the frictional contact forceZ1 by a friction coefficient, the same effects as described above can beobtained.

Example 3

Regarding Example 3, a description of parts common to Example 1 will beomitted, and only different points will be described. In Example 1, thefirst guide member 6, the vibrator 1, and the second guide member 16 aresequentially arranged in the Y direction. On the other hand, in Example3, a second guide member 36, a first guide member 6, and a vibrator 1are sequentially arranged in the Y direction, as shown in FIGS. 7A to7E. More specifically, a moving member 34 is pressed by a press member33 in the −Z direction, and an auxiliary moving member 32 against whichthe press member 33 abuts is guided by the second guide member 36.

As for the above-described arrangement, using sizes L1 and L2 shown inFIG. 7D and considering the balance on the Y-Z plane of the movingmember 34, we obtainZ33=(L1/L2)×(Z31−Z32)  (v)Z34=((L1+L2)/L1)×Z33  (vi).

To simplify the calculation, the sizes L1 and L2 in FIG. 7D are assumedto be almost equal. Since a contact force Z32 is equal to a frictionalcontact force Z1 in magnitude, as in Example 1, the sum of a contactforce Z33 and a contact force Z34 is three times larger than thedifference between the frictional contact force Z1 and a biasing contactforce Z31. As a result, if the frictional contact force Z1 is almostequal to the biasing contact force Z31 in magnitude, the frictionalforce as the cause of a decrease in the driving force can be reduced, asin Example 1.

As described above, a vibration wave motor 10 having the arrangement ofExample 3 can use, as the guide method for the moving member 34, asliding guide capable of downsizing and simplifying the vibration wavemotor without decreasing the driving force, as in Example 1. Inaddition, the linear driving apparatus can also be downsized andsimplified. Note that in Example 3, the effects have been describedassuming that the sizes L1 and L2 are almost equal. However, even if thesizes L1 and L2 are different, the contact force Z33 and the contactforce Z34 are decided by equations (v) and (vi). Hence, since thefrictional force generated on the first guide member 6 and the secondguide member 36 has a value obtained by multiplying ((2×L1+L2)/L2) timesof the difference between the biasing contact force Z31 and thefrictional contact force Z1 by a friction coefficient, the same effectsas described above can be obtained.

Example 4

Regarding Example 4, a description of parts common to Example 3 will beomitted, and only different points will be described. In Example 3, thebiasing contact force Z31 is larger than the frictional contact forceZ1, and considering the balance on the X-Z plane of the moving member34, the contact force Z33 acts in the same direction as the biasingcontact force Z31. On the other hand, in Example 4, a biasing contactforce Z41 is smaller than a frictional contact force Z1, and consideringthe balance on the X-Z plane of a moving member 44, a contact force Z43acts in the same direction as the frictional contact force Z1, as shownin FIGS. 8A to 8E. In Example 4 in which such forces act, the movingmember 44 is pressed by a press member 43 in the +Z direction, and anauxiliary moving member 42 against which the press member 43 abuts isguided by a second guide member 46.

Even in the above-described arrangement, using sizes L1 and L2 shown inFIG. 8D and considering the balance on the Y-Z plane of the movingmember 44, we obtainZ43=(L1/L2)×(Z42−Z41)  (vii)Z44=((L1+L2)/L1)×Z43  (viii).

To simplify the calculation, the sizes L1 and L2 in FIG. 8D are assumedto be almost equal. Since a contact force Z42 is equal to the frictionalcontact force Z1 in magnitude, as in Example 3, the sum of the contactforce Z43 and a contact force Z44 is three times larger than thedifference between the frictional contact force Z1 and the biasingcontact force Z41. As a result, if the frictional contact force Z1 isalmost equal to the biasing contact force Z41 in magnitude, thefrictional force as the cause of a decrease in the driving force can bereduced, as in Example 1.

As described above, a vibration wave motor 10 having the arrangement ofExample 4 can use, as the guide method for the moving member 44, asliding guide capable of downsizing and simplifying the vibration wavemotor without decreasing the driving force, as in Example 1. Inaddition, the linear driving apparatus can also be downsized andsimplified. Note that in Example 4, the effects have been describedassuming that the sizes L1 and L2 are almost equal. However, even if thesizes L1 and L2 are different, the contact force Z43 and the contactforce Z44 are decided by equations (vii) and (viii). Hence, since thefrictional force generated on a first guide member 6 and the secondguide member 46 has a value obtained by multiplying ((2×L1+L2)/L2) timesof the difference between the biasing contact force Z41 and thefrictional contact force Z1 by a friction coefficient, the same effectsas described above can be obtained.

(First Modification)

FIGS. 9A and 9B show the first modification constituted using thevibration wave motor 10 of one of Examples 1 to 4 described above. FIG.9A is a partially enlarged view on a plane. FIG. 9B is a sectional viewtaken along a cut line IXB-IXB in FIG. 9A. According to the firstmodification, on the projections on the X-Y plane, the load center A ofthe distribution load of the frictional contact force Z1 and the loadcenter B of the distribution load of the biasing contact force Z11 arealigned in the Y direction perpendicular to the moving direction X andthe Z direction of the frictional contact force Z1 but are not alignedin the moving direction X.

That is, the load center A and the load center B do not coincide witheach other and are spaced apart from each other to a certain extent.Assume that this degree of separation is defined as a shift amount D1.Note that the shift amount D1 is emphatically shown. In thisarrangement, the value of the shift amount D1 is set small, and thecouple V2 shown in FIG. 9B is intentionally made to exist as a verysmall value. The presence of the very small couple V2 can shift backlasharound the moving member to one side, and hence the arrangement canobtain the effect of reducing the vibration of the moving member andpreventing the generation of unnecessary vibration and noise of theapparatus.

(Second Modification)

FIGS. 9C and 9D show the second modification constituted using thevibration wave motor 10 of one of Examples 1 to 4 described above. FIG.9C is a partially enlarged view on a plane. FIG. 9D is a partiallyenlarged view on the front. According to the second modification, on theprojections on the X-Y plane, the load center A of the distribution loadof the frictional contact force Z1 and the load center B of thedistribution load of the biasing contact force Z11 fall within the rangeof the outside shape of the vibrator 1 but are not aligned in both themoving direction X and the Y direction perpendicular to the movingdirection X.

That is, the load center A and the load center B do not coincide witheach other and are spaced apart from each other to a certain extent.Assume that as for this degree of separation, the shift amount D1 in theY direction perpendicular to both the load center A and the load centerB and a shift amount D2 in the moving direction X are defined. Note thatboth the shift amount D1 and the shift amount D2 are emphatically shown.In this arrangement, the value of the shift amount D2 is set small, andthe couple V1 shown in FIG. 9D is intentionally made to exist as a verysmall value. The presence of the very small couple V1 can shift backlasharound the moving member to one side, and hence the arrangement canobtain the effect of reducing the vibration of the moving member andpreventing the generation of unnecessary vibration and noise of theapparatus. As described above, even if the load center A of thedistribution load of the frictional contact force Z1 and the load centerB of the distribution load of the biasing contact force Z11 are notaligned in either or both of the moving direction X and the Y directionperpendicular to the moving direction X, similar effects can beobtained.

(Third Modification)

FIG. 10 shows the third modification in which a linear driving apparatusconstituted using the vibration wave motor 10 of one of Examples 1 to 4described above is applied to an optical apparatus. A driving targetbody 27 is a holding member that is driven by a driving force output bythe above-described vibration wave motor 10 and also holds an opticalelement used for a photographing apparatus or the like. The drivingtarget body 27 includes a support portion 27 a and guide holes 27 b and27 c. The guide holes 27 c on one side are guided along a guide shaft25, and the guide hole 27 b on the other side is guided along the firstguide member 6 provided in the vibration wave motor 10. The transmissionmember 18 engages with the support portion 27 a. According to thisarrangement, the number of components can be reduced, and the apparatuscan be simplified. In addition, since the driving target body 27 sharesthe first guide member 6 used by the vibration wave motor 10 as a guidemember, it is possible to obtain the effect of improving the linearmotion accuracy. In the third modification as well, other arrangementscan be selected.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2015-227408, filed Nov. 20, 2015, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A linear driving apparatus comprising: avibration wave motor including: a vibrator having a piezoelectricelement configured to generate a vibration; a friction member configuredto come into contact with a protruding portion provided on the vibrator;a moving member movable in a predetermined moving direction with respectto the friction member; a coupling member configured to couple thevibrator and the moving member with each other; a first guide memberconfigured to guide the moving member in the moving direction; a pressmember configured to act on the moving member and capable of moving inthe predetermined moving direction together with the moving member; anda second guide member configured to guide the press member in thepredetermined moving direction; a driving target body movable in thepredetermined moving direction; a transmission member configured toengage with the driving target body, abut against an abutment part ofthe moving member, and transmit a driving force of the vibration wavemotor to the driving target body; and a biasing member configured toapply a biasing force between the transmission member and the abutmentpart, wherein a direction of a frictional contact force that thevibrator receives from the friction member and a direction of a biasingcontact force that the abutment part receives from the biasing memberare parallel and opposite, and a load center of a distribution load ofthe biasing contact force exists in a range of an outside shape of thevibrator.
 2. An apparatus according to claim 1, wherein an auxiliarymoving member is provided between the press member and the second guidemember.
 3. An apparatus according to claim 1, wherein on a planeperpendicular to the direction of the frictional contact force, a loadcenter of a distribution load of the frictional contact force and theload center of the distribution load of the biasing contact force arealigned in a direction perpendicular to both the predetermined movingdirection and the direction of the frictional contact force.
 4. Anapparatus according to claim 1, wherein on a plane perpendicular to thedirection of the frictional contact force, a load center of adistribution load of the frictional contact force and the load center ofthe distribution load of the biasing contact force substantiallycoincide with each other.
 5. An apparatus according to claim 1, whereinthe first guide member guides the driving target body in thepredetermined moving direction.
 6. An apparatus according to claim 1,wherein the vibration is an ultrasonic vibration, and the vibration wavemotor comprises an ultrasonic motor configured to generate theultrasonic vibration.
 7. An apparatus according to claim 1, wherein thedriving target body comprises a holding member configured to hold anoptical element.
 8. A vibration wave motor comprising: a vibrator havinga piezoelectric element configured to generate a vibration; a frictionmember configured to come into contact with a protruding portionprovided on the vibrator; a first moving member movable in apredetermined moving direction with respect to the friction member; acoupling member configured to couple the vibrator and the first movingmember with each other; a first guide member configured to guide thefirst moving member in the predetermined moving direction; a pressmember configured to act on the first moving member and capable ofmoving in the predetermined moving direction together with the firstmoving member; and a second guide member configured to guide the pressmember in the predetermined moving direction.
 9. A motor according toclaim 8, wherein a second moving member is provided between the pressmember and the second guide member.
 10. A motor according to claim 9,wherein the press member is provided between the first moving member andthe second moving member.
 11. A motor according to claim 9, wherein thesecond moving member engages with the first moving member and is guidedin the predetermined moving direction by the second guide member.
 12. Amotor according to claim 8, wherein the second guide member comprisesone of a rail-shaped plate member, a round bar member, a frictionreducing sheet member, and a roller member.
 13. A motor according toclaim 8, wherein a size of the moving member in the predetermined movingdirection is not greater than a size of the vibrator in thepredetermined moving direction.
 14. A motor according to claim 8,wherein the vibration is an ultrasonic vibration, and the vibration wavemotor comprises an ultrasonic motor configured to generate theultrasonic vibration.
 15. A linear driving apparatus comprising: avibration wave motor of claim 8; a driving target body movable in thepredetermined moving direction; a transmission member configured toengage with the driving target body, abut against an abutment part ofthe first moving member, and transmit a driving force of the vibrationwave motor to the driving target body; and a biasing member configuredto apply a biasing force between the transmission member and theabutment part.
 16. An apparatus according to claim 15, wherein the firstguide member guides the driving target body in the predetermined movingdirection.
 17. An optical apparatus using a linear driving apparatus ofclaim 15, wherein the driving target body comprises a holding memberconfigured to hold an optical element.